1. Field of the Invention
The present invention relates to a microorganism multiplication preventing method and apparatus for preventing the multiplication of microorganisms existing on the surface of objects in which the multiplication preventing of microorganisms is needed from the viewpoint of public health, such as foods, cooking utensils and other required tools related to foods, and for preventing the multiplication of microorganisms existing in a space for housing these objects' by using activated particles such as ions or ozone.
2. Description of Related Art
FIG. 14 is a structural drawing showing the microorganism multiplication preventing apparatus disclosed in Japanese Patent Laid-Open No. 7-115946. In FIG. 14, numerals 1 denote outdoor gas, the apparatus comprises a fan (ventilator) 2 for drawing the gas 1, a vent passage 3 for allowing the gas 1 drawn by the fan 2 to flow and a supply port 4 provided on the outdoor side of the fan 2 for drawing the gas 1. Further the apparatus comprises an ionization chamber 5 provided in the vent passage 3 for ionizing the drawn gas 1 by electrically detaching electrons, a bushing 6 provided in the vent passage 3 and made of insulating materials, metal needle electrodes 7 protruding into the passage duct 3 and made of metallic material such as tungsten, stainless steel or nickel, a metal plate 8 ground electrode placed in the vent passage 3 opposite the metal needle electrodes 7, and a plate dielectric 9 made of dielectric material, attached onto the metal plate ground electrode 8 by vapor deposition or close adhesion, such as ceramic, glass or quartz. Ionized gas containing ozone, ionized in the ionization chamber and flows through the vent passage 3 and an ozone decomposition chamber 11 filled with an ozone dissociating catalyzer, such as manganese dioxide or activated alumina, for decomposing the ozone contained in the ozone-contained gas 10 having been ionized in the ionization chamber 5. The ozone decomposition chamber 11 removes the ozone from the ozone-contained ionized gas 10. Furthermore, numeral 14 denotes objects placed in the ion treatment chamber, mentioned later, on which microoganisms multiply, the apparatus comprising an insulator 12 for electrically insulating the ozone decomposing chamber 11 from the vent passage 3, the ozone-free ionized gas 13 being sent from the vent passage 3 in the ion treatment chamber 15, mentioned later, the ion treatment chamber 15 having space enough for housing the objects for microorganisms to multiply thereon, to which the ozone-free ionized gas 13 is supplied after removal of ozone in the ozone decomposition chamber 11. The apparatus further comprises a high-voltage generator 16 for applying a high voltage between the metal needle electrodes 7 and the metal plate ground electrode 8, a gas inlet 17 for supplying the ozone-free ionized gas 13 to the ion treatment chamber 15 and a gas outlet 18 for releasing the used ozone-free ionized gas 13 to outside the ion treatment chamber 15, respectively.
Next, the operation will be described.
First, outdoor gas 1 is drawn from the supply port 4 by the fan 2 and led through the vent passage 3 into the ionization chamber 5.
In this ionization chamber 5, a plurality of metal needle electrodes 7 and a metal plate ground electrode 8 attached by close adhesion to the dielectric 9 placed opposite the metal needle electrodes 7, are disposed with a space (gap length) between both electrodes 7, 8 set at several millimeters. On application of an AC high voltage of several kV between both electrodes 7, 8, a high electric field is generated near the top of metal needle electrodes 7 and an electric discharge, known as a corona discharge, takes place.
When the gas 1 is led into the ionization chamber 5, oxygen molecules and other particles contained in the gas 1 collide with electrons so that oxygen molecules and other particles are ionized and consequently ions are contained in the gas 1.
However, since oxygen molecules are contained in the outdoor gas 1, ozone is also generated at the same time when ions are generated. Incidentally, because of its high oxidation power, this ozone is harmful if its concentration becomes high.
Accordingly, downstream in the vent passage 3, an ozone dissociation catalyzer, electrically insulated from the vent passage 3, is placed in the ozone dissociation chamber 11 and ozone is removed from the ozone-contained ionized gas 10 by using this ozone dissociation catalyzer to produce a ozone-free ionized gas 13.
The ozone-free ionized gas 13 produced in this manner is supplied to the ion treatment chamber 15 having a space for housing objects 14 for microorganisms to multiply thereon, to prevent the microorganisms stuck on the objects 14 from multiplying.
A conventional microorganism multiplication preventing apparatus is thus arranged and the ions generated in this apparatus are effective to prevent the multiplication of microorganisms. However, the generation amount of ions is limited and the self dissociation of ions increases with higher ion concentration in the gas, so that there is a problem that a high concentration of ions cannot be sufficiently supplied to the microorganisms stuck on the object. Another problem is that when the ion treatment stops, the multiplication starts again because only the ions are used. Therefore satisfactory effects on the prevention of microorganism multiplication are not obtained.
On the other hand, if ozone is used to prevent the multiplication of microorganisms, treatment with an ozone concentration of 0.1 ppm or higher is required, but in the region of concentration of 0.1 ppm or higher, the high oxidization power of the ozone causes a problem that, for example, some foods are discolored/denatured or equipment parts corrode.